Gut microbiome and innate immune response patterns in IgE-associated eczema

Probiotics in infants for prevention of allergic disease

RATIONALE

This is an update of a Cochrane review first published in 2007. Allergic disease and food allergy are prevalent, and contribute to a significant burden of disease on the individual, their family and the healthcare system. Probiotics are live bacteria that colonise the gastrointestinal tract, and have been studied in many clinical trials for preventing allergic conditions.

OBJECTIVES

To evaluate the benefits and harms of a probiotic, or a probiotic with added prebiotic ('synbiotic'), compared with control (placebo or no treatment) for preventing allergic diseases (asthma, eczema, allergic rhinitis) and dietary allergies in infants by two years of age.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase and trial registries in December 2023. We reviewed the reference lists of studies selected for inclusion in this review, and systematic reviews on similar topics. We manually searched conference abstracts.

ELIGIBILITY CRITERIA

We included randomised controlled trials that compared a probiotic to a control, or a probiotic added to a prebiotic ('synbiotic'). We included enterally fed infants in the first six months of life without clinical evidence of allergic disease. We included probiotics added to human milk or infant formula, added in the manufacturing process or given separately.

OUTCOMES

Infant incidence by two years of age and childhood incidence (up to 10 years of age or up to the age of latest report between 2 and 10 years) of specific allergic diseases, including: asthma, eczema, allergic rhinitis, immunoglobulin E (IgE)-mediated food allergy, IgE-mediated cow's milk protein allergy. Events of anaphylaxis and potential harms including adverse effects, harms or infection with probiotic bacteria.

RISK OF BIAS

We used the Cochrane RoB 2 tool to assess bias in the studies.

SYNTHESIS METHODS

We used the random-effects (Mantel-Haenszel) model for meta-analysis where possible. Where this was not possible due to the nature of the data, we synthesised and interpreted individual studies separately. We used GRADE to assess the certainty of evidence for each outcome.

INCLUDED STUDIES

We included 24 studies (7077 mother-infant pairs). The studies were conducted in many parts of the world, including the USA, Europe, South Korea, Japan, Singapore and Australia, with most being conducted in Europe. Studies were published between 2001 and 2020. As some studies measured outcomes such as eczema using different criteria, we made assumptions to allow us to combine data.

SYNTHESIS OF RESULTS

Probiotics may result in little to no difference in asthma (risk ratio (RR) 0.96, 95% confidence interval (CI) 0.65 to 1.44; 4 studies, 954 participants; low-certainty evidence), allergic rhinitis (RR 0.89, 95% CI 0.45 to 1.77; 5 studies, 1045 participants; low-certainty evidence) and IgE-mediated cow's milk protein allergy (RR 0.99, 95% CI 0.82 to 1.20; 4 studies, 259 participants; low-certainty evidence) by two years of age. Probiotics may result in a slight reduction in eczema by two years of age (RR 0.87, 95% CI 0.78 to 0.97; 18 studies, 3494 participants; low-certainty evidence); however, sensitivity analysis of the studies at low risk of bias showed little or no difference in eczema by two years of age (RR 0.86, 95% CI 0.69 to 1.07; 4 studies, 892 participants). Probiotic supplementation may have little to no effect on the incidence of food allergy by two years, but the evidence is very uncertain (RR 1.12, 95% CI 0.57 to 2.20; 3 studies, 857 participants; very low-certainty evidence). The evidence is very uncertain about the effect of synbiotics on eczema by two years of age (RR 0.88, 95% CI 0.52 to 1.47; 3 studies, 1235 participants; very low-certainty evidence). Synbiotics may result in little to no difference in food allergy by two years of age (RR 1.06, 95% CI 0.55 to 2.07; 1 study, 223 participants; low-certainty evidence). There were no data for the effect of synbiotics on asthma, allergic rhinitis and IgE-mediated cow's milk protein allergy by two years of age. Probiotic or synbiotic supplementation may result in little to no difference in potential harms including adverse effects, harms or infection with probiotic bacteria at any point during the study intervention by two years of age. There were no serious adverse events related to probiotics or synbiotics reported. We had some concerns about risk of bias for most studies, with only a few judged at low risk of bias. Some studies had a high risk of bias due to unclear randomisation, missing data and lack of prespecified intentions. Estimates were often imprecise, with wide CIs due to limited events. The limited data prevented subgroup analyses on infant risk factors and feeding methods for outcomes other than the effect of probiotics on eczema. Only three studies assessed synbiotic supplementation, leaving their role in allergic disease prevention uncertain. The included studies were mainly in high-income countries in many different areas of the world, but may have limited applicability to other regions.

AUTHORS' CONCLUSIONS

There is insufficient evidence to make conclusions about the effect of probiotics and synbiotics on preventing the development of allergic diseases by two years of age and during childhood up to 10 years of age. Although there were no serious adverse events reported for the use of probiotics in infants, incorporating probiotics and synbiotics into routine practice requires further information to support their use.

FUNDING

This Cochrane review had no dedicated funding.

REGISTRATION

Protocol (2007) available via https://doi.org/10.1002/14651858.CD006475. Original review (2007) available via https://doi.org/10.1002/14651858.CD006475.pub2.

Microbiome and pediatric leukemia, diabetes, and allergies: Systematic review and meta-analysis

BACKGROUND

Despite the different pathologies and genetic susceptibilities of childhood ALL, T1DM and allergies, these conditions share epidemiological risk factors related to timing of infectious exposures and acquisition of the gut microbiome in infancy. We have assessed whether lower microbiome diversity (Shannon Index) and shared genus/species profiles are associated with pediatric ALL, allergies, and T1DM.

METHODS AND FINDINGS

Literature search was performed using PubMed, Embase, Cochrane, and Web of Science databases. Case-control, meta-analyses, and cohort studies were considered for inclusion. Inclusion criteria: (i) subjects age 1-18 years at diagnosis, (ii) reports effect of microbiome measured prior to/at time of diagnosis/first intervention (iii) outcome of ALL, allergies, asthma, or T1DM, (iv) English text. Exclusion criteria: (i) age < 1 or >18 years at diagnosis, (ii) Down Syndrome-associated ALL, (iii) non-English text, (iv) reviews, pre-print, or abstracts, (v) heavily biased studies. Abstract and full text screening were performed by two independent reviewers. Data extraction was performed by one reviewer following PRISMA guidelines. Data were pooled using a random-effects model. Eighty-eight studies were included in the analysis, with seventy-seven in the qualitative analysis and 54 in the meta-analysis. Cases were found to have lower alpha-diversity than controls in ALL (SMD:-0.78, 95%CI:-1.21, -0.34), T1DM (SMD:-1.26, 95%CI:-3.49, 0.96), eczema (SMD:-0.34, 95%CI:-0.56, -0.12), atopy (SMD:-0.06, 95%CI:-0.34, 0.22), asthma (SMD:-0.37, 95%CI:-1.16, 0.42), and food allergy (SMD:-0.11, 95%CI:-0.63, 0.41).

CONCLUSIONS

These results highlight similarities in the microbiome diversity and composition of children with ALL, T1DM, and allergies. This is compatible with a common risk factor related to immune priming in infancy and highlights the gut microbiome as a potentially modifiable risk factor and preventative strategy for these childhood diseases.

Skin and systemic infections in children with atopic dermatitis: review of the current evidence

Atopic dermatitis is a chronic, pruritic inflammatory skin disorder that affects approximately 2%-42% of children worldwide. Its course is frequently complicated by secondary bacterial, viral, and fungal infections, which can exacerbate disease severity and hinder treatment outcomes. These infections are thought to arise due to a disrupted skin barrier, reduced antimicrobial peptide production, alterations in the skin microbiome, and Th2-dominant inflammatory response. Identifying the most prevalent and pathogenic microorganisms in patients with AD is critical for early diagnosis, effective management, and prevention of complications. This review provides an updated synthesis of current knowledge on the infectious agents implicated in AD pathogenesis, summarizing recent findings on the epidemiology, microbial interactions, and immune mechanisms involved. Furthermore, it provides an overview of the latest therapeutic strategies for managing AD and its associated infections. By integrating recent insights into pathogenesis and treatment, this study offers a comprehensive perspective on the evolving landscape of AD management in children.

Compositional and Functional Profile of Gut Microbiota in a Cohort of Adult Spanish Patients with Atopic Dermatitis Using Metagenomics: A Cross-Sectional Study

Background: The role of gut dysbiosis in the pathophysiology of atopic dermatitis (AD) through immune system (IS) imbalance is a novel line of investigation currently under discussion. This study aimed to characterize compare the composition and functional profile of the gut microbiota (GM) between adults with AD and healthy individuals. Methods: Observational cross-sectional study, where fecal samples from 70 adults (38 patients and 32 controls) were analyzed using metagenomics and bioinformatics. Results: Differences between the GM of patients with AD and healthy individuals were demonstrated. Reduced microbial diversity was found in subjects with AD. Bacterial species with lower abundance primarily belonged to the families Ruminococcaceae, Akkermansiaceae, and Methanobacteriaceae. Several microbial metabolic pathways were found to be decreased in patients with AD, including amino acid biosynthesis, vitamin biosynthesis, fatty acids and lipids biosynthesis, and energy metabolism. Conclusion: Adults with AD exhibited a distinct GM compared to healthy individuals. Changes were demonstrated both compositionally and functionally. Further investigation is mandatory to elucidate the potential link and causal relationship between gut dysbiosis and AD, which may be crucial for a deeper understanding of the disease's pathophysiology and the development of novel therapeutic approaches.

Exploring Causal Relationships Between Gut Microbiota, Inflammatory Cytokines, and Inflammatory Dermatoses: A Mendelian Randomization Study

Background

Some studies have established a link between gut microbiota, inflammatory proteins, and inflammatory dermatoses. However, the mediating role of inflammatory proteins in the gut-skin axis remains unclear.

Methods

Data on inflammatory proteins and gut microbiota were drawn from the GWAS catalog and MiBioGen consortium, with inflammatory skin disease data provided by the FinnGen consortium. Using genome-wide association studies (GWAS), we performed linkage disequilibrium score regression (LDSC) to assess genetic correlations and conducted a two-step Mendelian Randomization (MR) analysis to investigate circulating inflammatory proteins as potential mediators between gut microbiota and inflammatory dermatoses.

Results

MR analysis identified 38 gut microbiota and 23 inflammatory proteins associated with inflammatory skin diseases. After false discovery rate (FDR) correction, four gut microbiota taxa-Eubacterium fissicatena, Bacteroidaceae, Allisonella, and Bacteroides, remained statistically significant (OR = 1.32, 95% CI: 1.16-1.50, adjusted P = 0.007; OR = 2.25, 95% CI: 1.48-3.42, adjusted P = 0.026; OR = 1.42, 95% CI: 1.18-1.70, adjusted P = 0.014; OR = 2.25, 95% CI: 1.48-3.42, adjusted P = 0.013), with only IL-18R1 significantly associated with eczema (OR = 1.05, 95% CI: 1.03-1.08, adjusted P = 0.017). Further mediation analysis showed that IL-15RA mediated 11% of the pathway between Veillonellaceae and eczema, while FGF19 mediated 6% of the pathway between genus LachnospiraceaeUCG001 and psoriatic arthritis.

Conclusion

These findings provide potential targets for therapeutic interventions in inflammatory skin diseases.

Toll-like receptors in atopic dermatitis: pathogenesis and therapeutic implications

Toll-like receptors (TLR), the key players of the innate immune system, contribute to the pathogenesis of atopic dermatitis (AD) through multiple pathways. TLRs play a crucial role in delaying barrier repair, promoting Th2-mediated dermatitis, shifting the response toward Th1 in the chronic phase, and contributing to the establishment of the itch-scratch cycle, as well as mediating the effects of UV radiation. The dysregulation of proinflammatory and immunomodulatory effects of TLRs can be attributed to their ligand structures, receptor heterodimerization, the relative frequency of each TLR, interactions with other receptors/signalling pathways, cytokine milieu, and genetic polymorphisms. Current AD treatments like vitamin-D analogs, tacrolimus, and cyclosporine partially work through TLR modulation. Direct TLR stimulation using different compounds has shown therapeutic benefits in preclinical studies. However, significant challenges exist, including off-target effects due to ubiquitous TLR expression and complex roles in immune responses. Future directions include CRISPR-based gene editing to understand TLR functions, development of specific TLR modulators for targeted therapy, and machine learning applications to predict drug responses and identify novel ligands. Patient heterogeneity, including the presence or absence of polymorphisms, variations in TLR expression levels, and differences in immune responses, underscores the need for personalized therapeutic approaches.

Exploring the causal relationship between gut microbiota and atopic dermatitis: A Mendelian randomization study

Accumulating evidence indicates a correlation between gut microbiota (GM) and atopic dermatitis (AD). Nevertheless, the causal relationship between specific pathogenic bacterial taxa and AD remains uncertain. This investigation utilized a two-sample Mendelian randomization (MR) analysis to assess the causal association between GM and AD, identifying the most influential GM taxa. An MR study was conducted utilizing summary statistics derived from genome-wide association studies encompassing 207 GM taxa and their association with AD risk. The genome-wide association studies summary statistics for 207 GM taxa (from phylum to species level) were generated by the Dutch Microbiome Project. The genetic variants (P < 1 × 10-5) correlated with GM (n = 7738) were identified from this investigation. Additionally, 4 supplementary MR approaches, simple mode, MR-Egger, weighted mode, and weighted median, supported the inverse-variance weighted approach. Furthermore, sensitivity analyses were executed using leave-one-out analysis, Cochran Q test, MR-Egger intercept test, MR pleiotropy residual sum and outlier global test, and MR Steiger test. The MR analysis identified 17 distinct bacterial taxa involving 2 orders, 4 families, 5 genera, and 6 species. The inverse-variance weighted method demonstrated that 6 bacterial taxa were positively associated with AD. These taxa included the order Pasteurellales, family Burkholderiales noname, family Pasteurellaceae, genus Burkholderiales noname, species Burkholderiales bacterium_1_1_47, and species Desulfovibrio piger. Eleven bacterial taxa were negatively associated with AD, comprising the order Actinomycetales, family Micrococcaceae, family Oscillospiraceae, genus Rothia, genus Collinsella, genus Oscillibacter, genus Pseudoflavonifractor, species Oscillibacter_unclassified, species Roseburia hominis, species R mucilaginosa, and species Parabacteroides merdae. Moreover, the MR-Egger intercept test and MR pleiotropy residual sum and outlier global test validated that the MR analysis remained unaffected by horizontal pleiotropy (P > .05). Furthermore, the leave-one-out analysis contributed to validating the robustness of the outcomes. Finally, an MR Steiger directionality test confirmed the assessment of potential causal direction (P < .001). This investigation identified specific intestinal flora causally associated with AD risk, offering novel insights for future investigations and innovative avenues for AD diagnosis, therapeutic intervention, and prognostic assessment.

The Association between Gut Microbiota and Serum Biomarkers in Children with Atopic Dermatitis

Background. Currently, it is known that the gut microbiota plays an important role in the functioning of the immune system, and a rebalancing of the bacterial community can arouse complex immune reactions and lead to immune-mediated responses in an organism, in particular, the development of atopic dermatitis (AD). Cytokines and chemokines are regulators of the innate and adaptive immune response and represent the most important biomarkers of the immune system. It is known that changes in cytokine profiles are a hallmark of many diseases, including atopy. However, it remains unclear how the bacterial imbalance disrupts the function of the immune response in AD. Objectives. We attempted to determine the role of gut bacteria in modulating cytokine pathways and their role in atopic inflammation. Methods. We sequenced the 16S rRNA gene from 50 stool samples of children aged 3-12 years who had confirmed atopic dermatitis, and 50 samples from healthy children to serve as a control group. To evaluate the immune status, we conducted a multiplex immunofluorescence assay and measured the levels of 41 cytokines and chemokines in the serum of all participants. Results. To find out whether changes in the composition of the gut microbiota were significantly associated with changes in the level of inflammatory cytokines, a correlation was calculated between each pair of bacterial family and cytokine. In the AD group, 191 correlations were significant (Spearman's correlation coefficient, p ≤ 0.05), 85 of which were positive and 106 which were negative. Conclusions. It has been demonstrated that intestinal dysbiosis is associated with alterations in cytokine profiles, specifically an increase in proinflammatory cytokine concentrations. This may indicate a systemic impact of these conditions, leading to an imbalance in the immune system's response to the Th2 type. As a result, atopic conditions may develop. Additionally, a correlation between known AD biomarkers (IL-5, IL-8, IL-13, CCL22, IFN-γ, TNF-α) and alterations in the abundance of bacterial families (Pasteurellaceae, Barnesiellaceae, Eubacteriaceae) was observed.

Unlocking the Potential of Probiotics: A Comprehensive Review on Research, Production, and Regulation of Probiotics

This review provides a comprehensive overview of the current state of probiotic research, covering a wide range of topics, including strain identification, functional characterization, preclinical and clinical evaluations, mechanisms of action, therapeutic applications, manufacturing considerations, and future directions. The screening process for potential probiotics involves phenotypic and genomic analysis to identify strains with health-promoting properties while excluding those with any factor that could be harmful to the host. In vitro assays for evaluating probiotic traits such as acid tolerance, bile metabolism, adhesion properties, and antimicrobial effects are described. The review highlights promising findings from in vivo studies on probiotic mitigation of inflammatory bowel diseases, chemotherapy-induced mucositis, dysbiosis, obesity, diabetes, and bone health, primarily through immunomodulation and modulation of the local microbiota in human and animal models. Clinical studies demonstrating beneficial modulation of metabolic diseases and human central nervous system function are also presented. Manufacturing processes significantly impact the growth, viability, and properties of probiotics, and the composition of the product matrix and supplementation with prebiotics or other strains can modify their effects. The lack of regulatory oversight raises concerns about the quality, safety, and labeling accuracy of commercial probiotics, particularly for vulnerable populations. Advancements in multi-omics approaches, especially probiogenomics, will provide a deeper understanding of the mechanisms behind probiotic functionality, allowing for personalized and targeted probiotic therapies. However, it is crucial to simultaneously focus on improving manufacturing practices, implementing quality control standards, and establishing regulatory oversight to ensure the safety and efficacy of probiotic products in the face of increasing therapeutic applications.

The association of infant and mother gut microbiomes with development of allergic diseases in children: a systematic review

OBJECTIVE

It is believed that gut microbiota alteration leads to both intestinal and non-intestinal diseases in children. Since infants inherit maternal microbiota during pregnancy and lactation, recent studies suggest that changes in maternal microbiota can cause immune disorders as well. This systematic review was designed to assess the association between the child and mother's gut microbiome and allergy development in childhood.

DATA SOURCES

In this systematic review, international databases including PubMed, Scopus, and ISI/WOS were searched until January 2023 to identify relevant studies.

STUDY SELECTIONS

Observational studies that analyzed infant or maternal stool microbiome and their association with allergy development in children were included in this study. Data extraction and quality assessment of the included studies were independently conducted by two researchers.

RESULTS

Of the 1694 papers evaluated, 21 studies examined neonate gut microbiome by analyzing stool samples and six studies examined maternal gut microbiota. A total of 5319 participants were included in this study. Asthma followed by eczema and dermatitis were the most common allergy disorders among children. Urbanization caused a lack of diversity in the bacterial microbiota as well as lower levels of Bifidobacterium and Lachnospira associated with a higher risk of allergy. In contrast, higher levels of Roseburia and Flavonifractor were associated with lower allergy risk.

CONCLUSIONS

This systematic review shows that gut microbiota may be associated with allergy development. Further studies are required to provide a definitive answer.

Skin exposure to soil microbiota elicits changes in cell-mediated immunity to pneumococcal vaccine

A resilient immune system is characterized by its capacity to respond appropriately to challenges, such as infections, and it is crucial in vaccine response. Here we report a paired randomized intervention-control trial in which we evaluated the effect of microbially rich soil on immune resilience and pneumococcal vaccine response. Twenty-five age and sex matched pairs of volunteers were randomized to intervention and control groups. The intervention group rubbed hands three times a day in microbially rich soil until participants received a pneumococcal vaccine on day 14. Vaccine response, skin and gut bacteriome and blood cytokine levels were analyzed on days 0, 14 and 35. Peripheral blood mononuclear cells (PBMCs) were stimulated with vaccine components and autoclaved soil for cytokine production. Commensal bacterial community shifted only in the intervention group during the 14-day intervention period. When PBMCs collected on day 14 before the vaccination were stimulated with the vaccine components, IFN-y production increased in the intervention but not in the control group. On day 35, vaccination induced a robust antibody response in both groups. In parallel, gut bacterial community was associated with TGF-β plasma levels and TGF-β decrease in plasma was lower in the intervention group. The results indicate that exposure to microbially rich soil can modulate the cell-mediated immunity to components in pneumococcal vaccine.

Development of systemic and mucosal immune responses against gut microbiota in early life and implications for the onset of allergies

The early microbial colonization of human mucosal surfaces is essential for the development of the host immune system. Already during pregnancy, the unborn child is prepared for the postnatal influx of commensals and pathogens via maternal antibodies, and after birth this protection is continued with antibodies in breast milk. During this critical window of time, which extends from pregnancy to the first year of life, each encounter with a microorganism can influence children's immune response and can have a lifelong impact on their life. For example, there are numerous links between the development of allergies and an altered gut microbiome. However, the exact mechanisms behind microbial influences, also extending to how viruses influence host-microbe interactions, are incompletely understood. In this review, we address the impact of infants' first microbial encounters, how the immune system develops to interact with gut microbiota, and summarize how an altered immune response could be implied in allergies.

The Role of the Microbiota in the Pathogenesis and Treatment of Atopic Dermatitis-A Literature Review

Atopic dermatitis (AD) is a chronic inflammatory skin condition with a high prevalence worldwide. AD pathogenesis is complex and consists of immune system dysregulation and impaired skin barrier, influenced by genetic and environmental factors. The purpose of the review is to show the complex interplay between atopic dermatitis and the microbiota. Human microbiota plays an important role in AD pathogenesis and the course of the disease. Dysbiosis is an important factor contributing to the development of atopic diseases, including atopic dermatitis. The gut microbiota can influence the composition of the skin microbiota, strengthening the skin barrier and regulating the immune response via the involvement of bacterial metabolites, particularly short-chain fatty acids, in signaling pathways of the gut-skin axis. AD can be modulated by antibiotic intake, dietary adjustments, hygiene, and living conditions. One of the promising strategies for modulating the course of AD is probiotics. This review offers a summary of how the microbiota influences the development and treatment of AD, highlighting aspects that warrant additional investigation.

Microbial perspective on the skin-gut axis and atopic dermatitis

Atopic dermatitis (AD) is a relapsing inflammatory skin condition that has become a global health issue with complex etiology and mounting prevalence. The association of AD with skin and gut microbiota has been revealed by virtue of the continuous development of sequencing technology and genomics analysis. Also, the gut-brain-skin axis and its mutual crosstalk mechanisms have been gradually verified. Accordingly, the microbiota-skin-gut axis also plays an important role in allergic skin inflammation. Herein, we reviewed the relationship between the microbiota-skin-gut axis and AD, explored the underlying signaling molecules and potential pathways, and focused on the potential mechanisms of probiotics, antimicrobial peptides (AMPs), coagulase-negative staphylococci transplantation, fecal microbiota transplantation, AMPs, and addition of essential fatty acids in alleviating AD, with the aim to provide a new perspective for targeting microbiota in the treatment of allergic skin inflammation.

Microbiome: Role in Inflammatory Skin Diseases

As the body's largest organ, the skin harbors a highly diverse microbiota, playing a crucial role in resisting foreign pathogens, nurturing the immune system, and metabolizing natural products. The dysregulation of human skin microbiota is implicated in immune dysregulation and inflammatory responses. This review delineates the microbial alterations and immune dysregulation features in common Inflammatory Skin Diseases (ISDs) such as psoriasis, rosacea, atopic dermatitis(AD), seborrheic dermatitis(SD), diaper dermatitis(DD), and Malassezia folliculitis(MF).The skin microbiota, a complex and evolving community, undergoes changes in composition and function that can compromise the skin microbial barrier. These alterations induce water loss and abnormal lipid metabolism, contributing to the onset of ISDs. Additionally, microorganisms release toxins, like Staphylococcus aureus secreted α toxins and proteases, which may dissolve the stratum corneum, impairing skin barrier function and allowing entry into the bloodstream. Microbes entering the bloodstream activate molecular signals, leading to immune disorders and subsequent skin inflammatory responses. For instance, Malassezia stimulates dendritic cells(DCs) to release IL-12 and IL-23, differentiating into a Th17 cell population and producing proinflammatory mediators such as IL-17, IL-22, TNF-α, and IFN-α.This review offers new insights into the role of the human skin microbiota in ISDs, paving the way for future skin microbiome-specific targeted therapies.

Identification of gut microbiota dysbiosis in bullous pemphigoid under different disease activity

Bullous pemphigoid (BP) is a severe autoimmune blistering disease affecting patients' quality of life. Gut microbiota (GM) dysbiosis have been investigated to be associated with multiple autoimmune diseases. However, the relationship between GM and BP onset and remission remains to be established by a systematic study. We conducted a study that enrolled 24 patients with BP onset (BP group), 24 patients under remission stage (BP-R group) and 24 healthy controls (HC group). We applied 16S rRNA sequencing on faecal samples and revealed a separation of the microbiota structure. At the family level, Lachnospiraceae, Prevotellaceae and Veillonellaceae were more abundant in the HC and BP-R groups, while Bacteroidaceae, Ruminococcaceae and Enterobacteriaceae were more abundant in the BP group. Bugbase analysis revealed the potentially pathogenic bacteria had an increasing trend in the BP group compared with the HC group and this variation vanished in the BP-R group. At the amplicon sequence variants (ASV) level, Bacteroides ovatus (ASV40) and Veillonella dispar (ASV140) significantly decreased, while Prevotella copri (ASV54) increased in the BP group compared to the HC and BP-R groups. The HC group and BP-R group shared similar abundance. Furthermore, by correlation analysis, we investigated key ASVs correlated with clinical parameters and found some discriminate biomarkers between the BP and BP-R groups. Our study established a dynamic GM profile in BP patients under different disease activity, providing a new direction to understand the role of GM in BP pathogenesis and therapeutic effects.

Fruit Pouch Consumption Does Not Associate with Early Manifestations of Allergic Disease

Consumption of acidic fruit pouches in infancy may damage the epithelial barrier in the gastrointestinal tract and is suggested to increase allergy risk. We aimed to explore if a high fruit pouch consumption is associated with a higher incidence of early allergic manifestations. We included 2959 parent-child dyads from the Swedish prospective, population-based NorthPop birth cohort study with parentally reported data on frequency of fruit pouch consumption at 9 months of age, as well as parentally reported eczema, wheeze, physician-diagnosed asthma, and food allergy in the first 18 months of life. Immunoglobulin E levels (IgE) in serum (n = 1792), as response to a food mix and an inhalant mix, were determined at age 18 months. Compared with no consumption, daily consumption of one or more pouches at 9 months of age was associated with inhalant sensitization (odds ratio (OR) 2.27, 95% confidence interval (CI) 1.06-4.87, n = 1792) but did not remain significant in the multivariable adjusted model (aOR 2.08, 95% CI 0.95-4.53, n = 1679). There were no associations between fruit pouch consumption and allergic manifestations at this young age. This study suggests that fruit pouch consumption is not associated with allergic phenotypes or IgE sensitization in early childhood.

Altered Gut Microbiota Composition Is Associated with Difficulty in Explicit Emotion Regulation in Young Children

Executive function (EF) consists of explicit emotion regulation (EER) and cognitive control (CC). Childhood EER in particular predicts mental and physical health in adulthood. Identifying factors affecting EER development has implications for lifelong physical and mental health. Gut microbiota (GM) has attracted attention as a potential biomarker for risk of physical and mental problems in adulthood. Furthermore, GM is related to brain function/structure, which plays a crucial role in emotional processing. However, little is known about how GM compositions are associated with the development of emotion regulation in early childhood. Therefore, in this study, we examined 257 children aged 3-4 to investigate links between GM and risk to EF. EF was measured using the Mother-Reported Behavior Rating Inventory of Executive Function-Preschool version. GM composition (alpha/beta diversity and genus abundance) was evaluated using 16S rRNA gene sequencing and compared between EF-risk and non-risk groups. Our results show that children with EER-risk (an index of inhibitory self-control) had a higher abundance of the genera Actinomyces and Sutterella. Although we have not established a direct link between GM and CC risk, our findings indicate that GM of preschoolers is closely associated with emotional processing and that EERrisk children have more inflammation-related bacteria.

Toll-like receptors: their roles in pathomechanisms of atopic dermatitis

The skin functions as a physical barrier and represents the first line of the innate immune system. There is increasing evidence that toll-like receptors (TLRs) are involved in the pathomechanisms of not only infectious diseases, but also non-infectious inflammatory diseases. Interestingly, it has been demonstrated that TLRs recognize both exogenous threats, e.g. bacteria and viruses, and endogenous danger signals related to inflammation, cell necrosis, or tissue damage. Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease, which is associated with impaired skin barrier function, increased skin irritability to non-specific stimuli, and percutaneous sensitization. The impairment of skin barrier function in AD allows various stimuli, such as potential allergens and pathogens, to penetrate the skin and activate the innate immune system, including TLR signaling, which can lead to the development of adaptive immune reactions. In this review, I summarize the current understanding of the roles of TLR signaling in the pathogenesis of AD, with special emphasis on skin barrier function and inflammation.

Mechanisms of Lung and Intestinal Microbiota and Innate Immune Changes Caused by Pathogenic Enterococcus Faecalis Promoting the Development of Pediatric Pneumonia

Bacterial pneumonia is the main cause of illness and death in children under 5 years old. We isolated and cultured pathogenic bacteria LE from the intestines of children with pneumonia and replicated the pediatric pneumonia model using an oral gavage bacterial animal model. Interestingly, based on 16srRNA sequencing, we found that the gut and lung microbiota showed the same imbalance trend, which weakened the natural resistance of this area. Further exploration of its mechanism revealed that the disruption of the intestinal mechanical barrier led to the activation of inflammatory factors IL-6 and IL-17, which promoted the recruitment of ILC-3 and the release of IL-17 and IL-22, leading to lung inflammation. The focus of this study is on the premise that the gut and lung microbiota exhibit similar destructive changes, mediating the innate immune response to promote the occurrence of pneumonia and providing a basis for the development and treatment of new drugs for pediatric pneumonia.

From gut to skin: exploring the potential of natural products targeting microorganisms for atopic dermatitis treatment

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease. Recent studies have revealed that interactions between pathogenic microorganisms, which have a tendency to parasitize the skin of AD patients, play a significant role in the progression of the disease. Furthermore, specific species of commensal bacteria in the human intestinal tract can have a profound impact on the immune system by promoting inflammation and pruritogenesis in AD, while also regulating adaptive immunity. Natural products (NPs) have emerged as promising agents for the treatment of various diseases. Consequently, there is growing interest in utilizing natural products as a novel therapeutic approach for managing AD, with a focus on modulating both skin and gut microbiota. In this review, we discuss the mechanisms and interplay between the skin and gut microbiota in relation to AD. Additionally, we provide a comprehensive overview of recent clinical and fundamental research on NPs targeting the skin and gut microbiota for AD treatment. We anticipate that our work will contribute to the future development of NPs and facilitate research on microbial mechanisms, based on the efficacy of NPs in treating AD.

Atopic Dermatitis: Beyond the Skin and Into the Gut

Atopic dermatitis (AD) is a common, chronic and recurring inflammatory skin disorder characterized by an intensely pruritic, eczematous dermatitis. The etiology of AD is thought to involve a combination of environmental, genetic, and immunologic factors. Emerging research has investigated factors that may impact individual risk for developing AD, disease severity, and treatment response. One component is the gut microbiome, which is considered to play an essential role in maintaining the homeostasis of several organ systems. The gut microbiome has been described as a major regulator of the "gut-skin axis," yet some studies have yielded conflicting evidence regarding the strength of the association of gut microbiota dysbiosis with AD. This review discusses recent insights into the role of the gut microbiome in AD pathogenesis and its interplay among other complex systems that govern the current assessments of and treatments for AD.

Unique Gut Microbiome Signatures among Adult Patients with Moderate to Severe Atopic Dermatitis in Southern Chinese

Imbalance of the immune system caused by alterations of the gut microbiome is considered to be a critical factor in the pathogenesis of infant eczema, but the exact role of the gut microbiome in adult atopic dermatitis (AD) patients remains to be clarified. To investigate the differences of the gut microbiome between adult AD patients and healthy individuals, stool samples of 234 adults, containing 104 AD patients and 130 healthy subjects, were collected for 16S rRNA gene amplicon. Altered structure and metabolic dysfunctions of the gut microbiome were identified in adult AD patients. Our results illustrated that the adult AD patients were more likely to have allergies, particularly non-food allergies. In addition, the gut microbiome composition of the AD and normal groups were considerably different. Moreover, Romboutsia and Clostridi-um_sensu_stricto_1 was enriched in the normal group, whereas Blautia, Butyricicoccus, Lachnoclostridium, Eubacterium_hallii_group, Erysi-pelatoclostridium, Megasphaera, Oscillibacter, and Flavonifractor dominated in the AD group. Additionally, purine nucleotide degradation pathways were significantly enriched in the AD group, and the enrichment of proteinogenic amino acid biosynthesis pathways was found in the normal group. This study provides insights into new therapeutic strategies targeting the gut microbiome for AD and evidence for the involvement of the gut-skin axis in AD patients.

Modulation of allergic contact dermatitis via gut microbiota modified by diet, vitamins, probiotics, prebiotics, and antibiotics

Allergic contact dermatitis is one of the most common recorded occupational diseases. There are many different substances that the skin comes into contact with on a daily basis and that can cause ACD, e.g., preservatives, surfactants, and antimicrobial agents. The development of a mouse model of ACD has provided insight into the immune mechanisms involved. Drugs used in the treatment of skin diseases have many side effects. Therefore, alternative methods of suppressing the immune response to reduce the symptoms of skin diseases are being sought. In recent years, high hopes have been placed on dietary modulation and supplementation to affect the intestinal microbial composition and promote anti-inflammatory responses. In addition, other studies have shown the crucial role of intestinal microbiota in many immune-mediated diseases. Recognition and characterization of pro- and anti-inflammatory nutrients and supplements may be crucial to support the treatment of diseases such as atopic dermatitis, acne vulgaris, psoriasis, and allergic contact dermatitis.

Pathogenesis of allergic diseases and implications for therapeutic interventions

Allergic diseases such as allergic rhinitis (AR), allergic asthma (AAS), atopic dermatitis (AD), food allergy (FA), and eczema are systemic diseases caused by an impaired immune system. Accompanied by high recurrence rates, the steadily rising incidence rates of these diseases are attracting increasing attention. The pathogenesis of allergic diseases is complex and involves many factors, including maternal-fetal environment, living environment, genetics, epigenetics, and the body's immune status. The pathogenesis of allergic diseases exhibits a marked heterogeneity, with phenotype and endotype defining visible features and associated molecular mechanisms, respectively. With the rapid development of immunology, molecular biology, and biotechnology, many new biological drugs have been designed for the treatment of allergic diseases, including anti-immunoglobulin E (IgE), anti-interleukin (IL)-5, and anti-thymic stromal lymphopoietin (TSLP)/IL-4, to control symptoms. For doctors and scientists, it is becoming more and more important to understand the influencing factors, pathogenesis, and treatment progress of allergic diseases. This review aimed to assess the epidemiology, pathogenesis, and therapeutic interventions of allergic diseases, including AR, AAS, AD, and FA. We hope to help doctors and scientists understand allergic diseases systematically.

Childhood Obesity and the Cryptic Language of the Microbiota: Metabolomics’ Upgrading

The growing obesity epidemic in childhood is increasingly concerning for the related physical and psychological consequences, with a significant impact on health care costs in both the short and the long term. Nonetheless, the scientific community has not yet completely clarified the complex metabolic mechanisms underlying body weight alterations. In only a small percentage of cases, obesity is the result of endocrine, monogenic, or syndromic causes, while in much more cases, lifestyle plays a crucial role in obesity development. In this context, the pediatric age appears to be of considerable importance as prevention strategies together with early intervention can represent important therapeutic tools not only to counteract the comorbidities that increasingly affect children but also to hinder the persistence of obesity in adulthood. Although evidence in the literature supporting the alteration of the microbiota as a critical factor in the etiology of obesity is abundant, it is not yet fully defined and understood. However, increasingly clear evidence is emerging regarding the existence of differentiated metabolic profiles in obese children, with characteristic metabolites. The identification of specific pathology-related biomarkers and the elucidation of the altered metabolic pathways would therefore be desirable in order to clarify aspects that are still poorly understood, such as the consequences of the interaction between the host, the diet, and the microbiota. In fact, metabolomics can characterize the biological behavior of a specific individual in response to external stimuli, offering not only an eventual effective screening and prevention strategy but also the possibility of evaluating adherence and response to dietary intervention.

Targeting the gut-lung axis by synbiotic feeding to infants in a randomized controlled trial

BACKGROUND

Formula-fed infants are at increased risk of infections. Due to the cross-talk between the mucosal systems of the gastrointestinal and respiratory tracts, adding synbiotics (prebiotics and probiotics) to infant formula may prevent infections even at distant sites. Infants that were born full term and weaned from breast milk were randomized to prebiotic formula (fructo- and galactooligosaccharides) or the same prebiotic formula with Lactobacillus paracasei ssp. paracasei F19 (synbiotics) from 1 to 6 months of age. The objective was to examine the synbiotic effects on gut microbiota development.

RESULTS

Fecal samples collected at ages 1, 4, 6, and 12 months were analyzed using 16S rRNA gene sequencing and a combination of untargeted gas chromatography-mass spectrometry/liquid chromatography-mass spectrometry. These analyses revealed that the synbiotic group had a lower abundance of Klebsiella, a higher abundance of Bifidobacterium breve compared to the prebiotic group, and increases in the anti-microbial metabolite d-3-phenyllactic acid. We also analyzed the fecal metagenome and antibiotic resistome in the 11 infants that had been diagnosed with lower respiratory tract infection (cases) and 11 matched controls using deep metagenomic sequencing. Cases with lower respiratory tract infection had a higher abundance of Klebsiella species and antimicrobial resistance genes related to Klebsiella pneumoniae, compared to controls. The results obtained using 16S rRNA gene amplicon and metagenomic sequencing were confirmed in silico by successful recovery of the metagenome-assembled genomes of the bacteria of interest.

CONCLUSIONS

This study demonstrates the additional benefit of feeding specific synbiotics to formula-fed infants over prebiotics only. Synbiotic feeding led to the underrepresentation of Klebsiella, enrichment of bifidobacteria, and increases in microbial degradation metabolites implicated in immune signaling and in the gut-lung and gut-skin axes. Our findings support future clinical evaluation of synbiotic formula in the prevention of infections and associated antibiotic treatment as a primary outcome when breastfeeding is not feasible.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01625273 . Retrospectively registered on 21 June 2012.

Combined microbiome and metabolome analysis of gut microbiota and metabolite interactions in chronic spontaneous urticaria

Background

The pathogenesis of chronic spontaneous urticaria (CSU) is unclear, and it turned out to be involved in biological processes, such as autoimmunity, autoallergy, inflammation, and coagulation. The gut microbiota plays an important role in immune and inflammatory diseases. However, the relationship between chronic spontaneous urticaria and the gut microbiota remains unknown.

Methods

The stool and serum samples were taken from 15 CSU patients and 15 normal controls. Changes in the composition of gut microbiota and serum metabolism in CSU patients and normal controls were analyzed by 16S ribosomal RNA (rRNA) gene sequencing and untargeted metabolomics.

Results

The results of 16S rRNA gene sequencing showed that compared with normal controls, CSU patients had increased α-diversity of gut microbiota and significant differences in β-diversity. At the phylum level, the relative abundance of Firmicutes increased and the relative abundance of Bacteroidetes and Proteobacteria decreased in CSU patients compared with healthy controls. At the genus level, six kinds of bacteria were significantly enriched in CSU patients and five in normal controls. Metabolomic analysis revealed altered levels of metabolites such as unsaturated fatty acids and purines. Correlation analysis of gut microbiota and metabolites showed that Lachnospira was negatively correlated with arachidonic acid, and Gemmiger was also negatively correlated with (±)8-HETE.

Conclusion

This study suggests that changes in gut microbiota and metabolites may play a role in immune and inflammatory pathways in the pathogenesis of CSU patients.

Ecology, Not Host Phylogeny, Shapes the Oral Microbiome in Closely Related Species

Host-associated microbiomes are essential for a multitude of biological processes. Placed at the contact zone between external and internal environments, the little-studied oral microbiome has important roles in host physiology and health. Here, we investigate the roles of host evolutionary relationships and ecology in shaping the oral microbiome in three closely related gorilla subspecies (mountain, Grauer's, and western lowland gorillas) using shotgun metagenomics of 46 museum-preserved dental calculus samples. We find that the oral microbiomes of mountain gorillas are functionally and taxonomically distinct from the other two subspecies, despite close evolutionary relationships and geographic proximity with Grauer's gorillas. Grauer's gorillas show intermediate bacterial taxonomic and functional, and dietary profiles. Altitudinal differences in gorilla subspecies ranges appear to explain these patterns, suggesting a close connection between dental calculus microbiomes and the environment, likely mediated through diet. This is further supported by the presence of gorilla subspecies-specific phyllosphere/rhizosphere taxa in the oral microbiome. Mountain gorillas show a high abundance of nitrate-reducing oral taxa, which may promote adaptation to a high-altitude lifestyle by modulating blood pressure. Our results suggest that ecology, rather than evolutionary relationships and geographic distribution, shape the oral microbiome in these closely related species.

Allergic Inflammation: Effect of Propolis and Its Flavonoids

The incidence of allergic diseases and their complications are increasing worldwide. Today, people increasingly use natural products, which has been termed a "return to nature". Natural products with healing properties, especially those obtained from plants and bees, have been used in the prevention and treatment of numerous chronic diseases, including allergy and/or inflammation. Propolis is a multi-component resin rich in flavonoids, collected and transformed by honeybees from buds and plant wounds for the construction and adaptation of their nests. This article describes the current views regarding the possible mechanisms and multiple benefits of flavonoids in combating allergy and allergy-related complications. These benefits arise from flavonoid anti-allergic, anti-inflammatory, antioxidative, and wound healing activities and their effects on microbe-immune system interactions in developing host responses to different allergens. Finally, this article presents various aspects of allergy pathobiology and possible molecular approaches in their treatment. Possible mechanisms regarding the antiallergic action of propolis on the microbiota of the digestive and respiratory tracts and skin diseases as a method to selectively remove allergenic molecules by the process of bacterial biotransformation are also reported.

Hygienic behaviors during the COVID-19 pandemic may decrease immunoglobulin G levels: Implications for Kawasaki disease

Background

Due to the coronavirus disease 2019 (COVID-19) pandemic, hygienic behaviors became a new norm since January 2020. The hygiene hypothesis predicts that an excessively hygienic environment may adversely affect human health.

Objective

We quantified the effect of COVID-19 on immunological parameters linked to the hygiene hypothesis.

Methods

We examined age-specific levels of total nonspecific immunoglobulin G (IgG) and IgE in individuals who visited Fukuoka Tokushukai Hospital between 2010 and 2021. Pre-COVID (2010–2019) and COVID (2020–2021) periods were compared.

Results

IgG levels steadily decreased throughout Pre-COVID period. IgG levels fell abruptly from the pre-COVID period to the COVID period in all age groups (P = 0.0271, < 0.3 years; P = 0.0096, 0.3–5 years; P = 0.0074, ≥ 5 years). The declines in IgG in < 0.3 years and that in ≥ 5 years accelerated during the COVID period. IgE levels were seasonal, but did not change noticeably from the pre-COVID to COVID period. IgG levels recorded for patients with Kawasaki disease (KD) (mean 709 mg/dL) were significantly lower than for matched control subjects (826 mg/dL) (P<0.0001).

Discussion

Hygienic behaviors during the COVID-19 outbreak decreased the chance of infection, which may explain the decreases in IgG levels in children and adults. Neonatal IgG declined, possibly because of the decrease in maternal IgG.

Conclusion

Hygienic behaviors decreased the IgG levels in all age groups, from neonates to adults. This downturn in IgG may lead to vulnerability to infections as well as to KD.

Comparison of the Gut Microbiome between Atopic and Healthy Dogs—Preliminary Data

Simple Summary

Atopic dermatitis is a common inflammatory and itchy skin disease, constituting a global issue that affects up to 15% of the general human and dog population. The pathogenesis of this disease is known to be multifactorial and not only consisting of skin barrier dysfunction, but also with immunological dysregulation and skin microbiota changes having a central role. In humans, establishment of the gut microbiota in early life influences the development of allergies, among others also atopic dermatitis in children. To the author’s knowledge, there is currently no study comparing the gut microbiome between allergic and healthy dogs. We now present results demonstrating that allergic dogs have a significantly different gut microbiota when compared to healthy control dogs. Further investigations including a larger number of dogs are now required to confirm these results, in addition to studies utilizing novel interventions targeting the gut microbiota.

Abstract

Human studies show that in addition to skin barrier and immune cell dysfunction, both the cutaneous and the gut microbiota can influence the pathogenesis of atopic diseases. There is currently no data on the gut-skin axis in allergic canines. Therefore, the aim of this study was to assess the bacterial diversity and composition of the gut microbiome in dogs with atopic dermatitis (AD). Stool samples from adult beagle dogs (n = 3) with spontaneous AD and a healthy control group (n = 4) were collected at Days 0 and 30. After the first sampling, allergic dogs were orally dosed on a daily basis with oclacitinib for 30 days, and then re-sampled. Sequencing of the V3–V4 region of the 16S rRNA gene was performed on the Illumina MiSeq platform and the data were analyzed using QIIME2. The atopic dogs had a significantly lower gut microbiota alpha-diversity than healthy dogs (p = 0.033). In healthy dogs, a higher abundance of the families Lachnospiraceae (p = 0.0006), Anaerovoracaceae (p = 0.006) and Oscillospiraceae (p = 0.021) and genera Lachnospira (p = 0.022), Ruminococcustorques group (p = 0.0001), Fusobacterium (p = 0.022) and Fecalibacterium (p = 0.045) was seen, when compared to allergic dogs. The abundance of Conchiformibius (p = 0.01), Catenibacterium spp. (p = 0.007), Ruminococcus gnavus group (p = 0.0574) and Megamonas (p = 0.0102) were higher in allergic dogs. The differences in alpha-diversity and on the compositional level remained the same after 1 month, adding to the robustness of the data. Additionally, we could also show that a 4-week treatment course with oclacitinib was not associated with changes in the gut microbiota diversity and composition in atopic dogs. This study suggests that alterations in the gut microbiota diversity and composition may be associated with canine AD. Large-scale studies preferably associated to a multi-omics approach and interventions targeting the gut microbiota are needed to confirm these results.

Associations between pre- and postnatal antibiotic exposures and early allergic outcomes: A population-based birth cohort study

BACKGROUND

Early life antibiotic treatment is one likely exposure influencing allergy risk. The objective was to investigate associations between pre- and postnatal antibiotic exposures and the development of allergic manifestations until age 18 months.

METHODS

We included 1387 mother-child dyads from the prospective, population-based NorthPop birth cohort study. Data on antibiotic exposures in pregnancy and childhood were collected by web-based questionnaires. Until the child turned 18 months old, parents (n = 1219) reported symptoms of wheeze, eczema, and physician-diagnosed asthma; parents (n = 1025) reported physician-diagnosed food allergy. At age 18 months, serum immunoglobulin E levels to inhalant (Phadiatop) and food (Food mix fx5) allergens were determined. Associations were estimated using bivariable and multivariable logistic regressions.

RESULTS

Prenatal antibiotic exposure was positively associated with food sensitization in the crude (OR 1.82, 95% CI 1.01-3.26) but not in the adjusted analyses (aOR 1.58, 0.82-3.05). A borderline significant association was found between prenatal exposure and wheeze (aOR 1.56, 0.95-2.57). Postnatal antibiotics were positively associated with wheeze (aOR 2.14, 1.47-3.11), asthma (aOR 2.35, 1.32-4.19), and eczema (aOR 1.49, 1.07-2.06). Postnatal antibiotics were negatively associated with food sensitization (aOR 0.46, 95% CI 0.25-0.83) but not with food allergy nor sensitization to inhalants.

CONCLUSION

Pre- and postnatal antibiotic exposure demonstrated positive associations with allergic manifestations and the former also with food sensitization. In contrast, there was a negative association between postnatal antibiotics and food sensitization. Food sensitization is often transient but may precede respiratory allergies. Future studies should investigate the relationship between antibiotic exposure and food sensitization later in childhood.

Exploring the Potential of Human Milk and Formula Milk on Infants’ Gut and Health

Early-life gut microbiota plays a role in determining the health and risk of developing diseases in later life. Various perinatal factors have been shown to contribute to the development and establishment of infant gut microbiota. One of the important factors influencing the infant gut microbial colonization and composition is the mode of infant feeding. While infant formula milk has been designed to resemble human milk as much as possible, the gut microbiome of infants who receive formula milk differs from that of infants who are fed human milk. A diverse microbial population in human milk and the microbes seed the infant gut microbiome. Human milk contains nutritional components that promote infant growth and bioactive components, such as human milk oligosaccharides, lactoferrin, and immunoglobulins, which contribute to immunological development. In an attempt to encourage the formation of a healthy gut microbiome comparable to that of a breastfed infant, manufacturers often supplement infant formula with prebiotics or probiotics, which are known to have a bifidogenic effect and can modulate the immune system. This review aims to elucidate the roles of human milk and formula milk on infants’ gut and health.

Pathways of atopic disease and neurodevelopmental impairment: assessing the evidence for infant antibiotics

INTRODUCTION

Epidemiologic studies are starting to report associations between antibiotic use in early life and neurodevelopmental disorders. Through mechanisms within the gut microbiota-brain axis, indeed, it is plausible that infant antibiotic treatment plays a role in the development of atopic disease and neurodevelopmental disorders.

AREAS COVERED

This narrative review summarizes and interprets published evidence on infant antibiotic use in future outcomes of atopic disease, and neurodevelopmental delay and disorders, including attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). To this end, we critically assess study bias from 2 main confounding factors, maternal/infant infection and infant feeding status. We also discuss common mechanisms that link atopy and neurodevelopment, and propose hypotheses related to immune activation and the gut microbiome.

EXPERT OPINION

Atopic disease and neurodevelopmental disorders share many risk factors and biological pathways. Infant antibiotic use has been linked to both disorders and is likely a marker for prenatal or infant infection. The mediating role of breastfeeding can also not be discounted. The exploration of causal pathways along the gut-brain axis leading towards neurodevelopmental impairment is evolving and of future interest.

D-galactose Intake Alleviates Atopic Dermatitis in Mice by Modulating Intestinal Microbiota

Atopic dermatitis (AD) is one of the most prevalent, chronic and persistent inflammatory skin diseases closely associated with intestinal microbiota. To evaluate the effect of D-galactose intake on AD, we orally administered D-galactose to BALB/c mice whose ears and skin were treated with 2,4-dinitrochlorobenzene (DNCB). D-galactose alleviated DNCB-induced AD-like phenotypes such as redness, scaling/dryness and excoriation. Ear thickness was also decreased by D-galactose administration. Histopathological analysis revealed decreased epidermal thickening, infiltration of immune cells, especially mast cells, in the dermis. Total levels of serum IgE representing the immunological response of AD were decreased by D-galactose administration. Microbiota analysis showed that D-galactose administration restored gut microbiota profiles, which were altered in AD mice, characterized by increased abundance of Bacteroidetes and decreased abundance of Firmicutes. The increased abundance of Bacteroides and the decreased abundance of Prevotella and Ruminococcus were reversed by D-galactose treatment, following improvement of AD. Our results suggest the possible use of D-galactose as a prebiotic to alleviate AD by altering gut microbiota.

The Role of Early Life Microbiota Composition in the Development of Allergic Diseases

Allergic diseases are becoming a major healthcare issue in many developed nations, where living environment and lifestyle are most predominantly distinct. Such differences include urbanized, industrialized living environments, overused hygiene products, antibiotics, stationary lifestyle, and fast-food-based diets, which tend to reduce microbial diversity and lead to impaired immune protection, which further increase the development of allergic diseases. At the same time, studies have also shown that modulating a microbiocidal community can ameliorate allergic symptoms. Therefore, in this paper, we aimed to review recent findings on the potential role of human microbiota in the gastrointestinal tract, surface of skin, and respiratory tract in the development of allergic diseases. Furthermore, we addressed a potential therapeutic or even preventive strategy for such allergic diseases by modulating human microbial composition.

Manipulating Microbiota to Treat Atopic Dermatitis: Functions and Therapies

Atopic dermatitis (AD) is a globally prevalent skin inflammation with a particular impact on children. Current therapies for AD are challenged by the limited armamentarium and the high heterogeneity of the disease. A novel promising therapeutic target for AD is the microbiota. Numerous studies have highlighted the involvement of the skin and gut microbiota in the pathogenesis of AD. The resident microbiota at these two epithelial tissues can modulate skin barrier functions and host immune responses, thus regulating AD progression. For example, the pathogenic roles of Staphylococcus aureus in the skin are well-established, making this bacterium an attractive target for AD treatment. Targeting the gut microbiota is another therapeutic strategy for AD. Multiple oral supplements with prebiotics, probiotics, postbiotics, and synbiotics have demonstrated promising efficacy in both AD prevention and treatment. In this review, we summarize the association of microbiota dysbiosis in both the skin and gut with AD, and the current knowledge of the functions of commensal microbiota in AD pathogenesis. Furthermore, we discuss the existing therapies in manipulating both the skin and gut commensal microbiota to prevent or treat AD. We also propose potential novel therapies based on the cutting-edge progress in this area.

Intestinal bacteria flora changes in patients with Mycoplasma pneumoniae pneumonia with or without wheezing

Mycoplasma pneumoniae (MP) infection is a common cause of community-acquired pneumonia in children. Furthermore, many children with Mycoplasma pneumoniae pneumonia (MPP) have recurrent wheezing and reduced small airway function after their clinical symptoms have resolved, eventually leading to asthma. MPP can trigger immune disorders and systemic inflammatory responses. Hence, the intestine is the largest immune organ of the body. Therefore, we sought to investigate whether the alteration of intestinal flora is correlated with the development of wheezing in children with MPP. We collected 30 healthy children as group A, 50 children with nonwheezing MPP as group B, and 50 children with wheezing MPP as group C. We found that the percentage of eosinophil cells (EC) was significantly higher in group C than that in group B for routine blood tests and serum inflammatory factors. The serum cytokines, including IL-4, IL-17, TNF-α, and TGF-β, were significantly higher in group C than in group B. In addition, the level of IL-10 was significantly lower in group C than in group B. The distribution characteristics of intestinal flora strains in children with MPP were detected by sequencing of 16S rRNA gene amplicon sequencing. There were differences in the abundance of intestinal flora between children with MPP and healthy children, with lower abundance of Ruminococcus flavefaciens, Clostridium butyricum, Lactobacillus, and Bifidobacterium in the intestine of children with MPP compared to healthy children. The abundance of Ruminococcus flavefaciens and Clostridium butyricum was significantly lower in the intestine of children with wheezing MPP compared to children without wheezing MPP. In the correlation analysis between children with MPP and inflammatory factors, Ruminococcus flavefaciens was found to be negatively correlated with IL-17. Clostridium butyricum was negatively correlated with L-4, IL-17, TNF-α, and TGF-β; however, it positively correlated with IL-10. Thus, it was concluded that alterations in intestinal flora play a crucial role in the immune response to MPP, where a significant decline in intestinal Ruminococcus flavefaciens and Clostridium butyricum leads to an exacerbation of the inflammatory responses, which may promote the development of children with wheezing MPP.

Gut dysbiosis in cutaneous T-cell lymphoma is characterized by shifts in relative abundances of specific bacterial taxa and decreased diversity in more advanced disease

BACKGROUND

Cutaneous T-cell lymphoma (CTCL) patients often suffer from recurrent skin infections and profound immune dysregulation in advanced disease. The gut microbiome has been recognized to influence cancers and cutaneous conditions; however, it has not yet been studied in CTCL.

OBJECTIVES

To investigate the gut microbiome in patients with CTCL and in healthy controls.

METHODS

Case-control study conducted between January 2019 and November 2020 at Northwestern's busy multidisciplinary CTCL clinic (Chicago, Illinois, USA) utilizing 16S ribosomal RNA gene amplicon sequencing and bioinformatics analyses to characterize the microbiota present in fecal samples of CTCL patients (n=38) and age-matched healthy controls (n=13) from the same geographical region.

RESULTS

Gut microbial α-diversity trended lower in patients with CTCL and was significantly lower in patients with advanced CTCL relative to controls (p=0.015). No differences in β-diversity were identified. Specific taxa were significantly reduced in patient samples; significance was determined using adjusted p-values (q-values) that accounted for a false discovery rate threshold of 0.05. Significantly reduced taxa in patient samples included the phylum Actinobacteria (q=0.0002), classes Coriobacteriia (q=0.002) and Actinobacteria (q=0.03), order Coriobacteriales (q=0.003), and genus Anaerotruncus (q=0.01). The families of Eggerthellaceae (q=0.0007) and Lactobacillaceae (q=0.02) were significantly reduced in patients with high skin disease burden.

CONCLUSIONS

Gut dysbiosis can be seen in patients with CTCL compared to healthy controls and is pronounced in more advanced CTCL. The taxonomic shifts associated with CTCL are similar to those previously reported in atopic dermatitis and opposite those of psoriasis, suggesting microbial parallels to the immune profile and skin barrier differences between these conditions. These findings may suggest new microbial disease biomarkers and reveal a new angle for intervention.

Classifying atopic dermatitis: a systematic review of phenotypes and associated characteristics

Atopic dermatitis is a heterogeneous disease, accompanied by a wide variation in disease presentation and the potential to identify many phenotypes that may be relevant for prognosis and treatment. We aimed to systematically review previously reported phenotypes of atopic dermatitis and any characteristics associated with them. Ovid EMBASE, Ovid MEDLINE and Web of Science were searched from inception till the 12th of February 2021 for studies attempting to classify atopic dermatitis. Primary outcomes are atopic dermatitis phenotypes and characteristics associated with them in subsequent analyses. A secondary outcome is the methodological approach used to derive them. In total, 8,511 records were found. By focusing only on certain clinical phenotypes, 186 studies were eligible for inclusion. The majority of studies were hospital-based (59%, 109/186) and cross-sectional (76%, 141/186). The number of included patients ranged from seven to 526,808. Data-driven approaches to identify phenotypes were only used in a minority of studies (7%, 13/186). Ninety-one studies (49%) investigated a phenotype based on disease severity. A phenotype based on disease trajectory, morphology and eczema herpeticum was investigated in 56 (30%), 22 (12%) and 11 (6%) studies, respectively. Thirty-six studies (19%) investigated morphological characteristics in other phenotypes. Investigated associated characteristics differed between studies. In conclusion, we present an overview of phenotype definitions used in literature for severity, trajectory, morphology and eczema herpeticum, including associated characteristics. There is a lack of uniform and consistent use of atopic dermatitis phenotypes across studies.

Perinatal origins of chronic lung disease: mechanisms-prevention-therapy-sphingolipid metabolism and the genetic and perinatal origins of childhood asthma

Childhood asthma derives from complex host-environment interactions occurring in the perinatal and infant period, a critical time for lung development. Sphingolipids are bioactive molecules consistently implicated in the pathogenesis of childhood asthma. Genome wide association studies (GWAS) initially identified a link between alleles within the 17q21 asthma-susceptibility locus, childhood asthma, and overexpression of the ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3), an inhibitor of de novo sphingolipid synthesis. Subsequent studies of pediatric asthma offer strong evidence that these asthma-risk alleles correlate with early-life aberrancies of sphingolipid homeostasis and asthma. Relationships between sphingolipid metabolism and asthma-related risk factors, including maternal obesity and respiratory viral infections, are currently under investigation. This review will summarize how these perinatal and early life exposures can synergize with 17q21 asthma risk alleles to exacerbate disruptions of sphingolipid homeostasis and drive asthma pathogenesis.

Altered gut microbiome compositions are associated with the severity of asthma

Background

Despite substantial evidence on the contribution of the diversity of the gut microbiome to the pathogenesis of asthma and allergic diseases, little is known about their relationship with asthma severity and/or clinical phenotypes. We analyzed the difference in composition of the gut microbiome between subjects with asthma and healthy subjects and explored its role in the development of asthma.

Methods

Fecal samples from 15 subjects with severe asthma (SA), 14 with non-severe asthma (NSA), and 15 healthy subjects were assessed by 16S ribosomal RNA gene sequencing methods to identify the gut bacterial composition.

Results

Compared with those in the NSA group, patients in the SA group had a higher dose of inhaled corticosteroids, and there were more atopic subjects (60% vs. 35.7%, respectively). No significant differences were found at the phylum level either in operational taxonomic unit numbers or in diversity scores among the SA, NSA, and healthy groups. However, at the family level, the relative abundance of Acidaminococcaceae in the SA group was remarkedly lower than that in the group with healthy subjects (P<0.05). Furthermore, Veillonellaceae and Prevotellaceae were significantly more common in samples from the SA group than in those from the NSA group (P<0.05). In the SA group, positive correlations were observed between the relative abundance of Veillonellaceae and mid-expiratory flow 25% (MEF25%) predicted (r=0.538, P=0.047), as well as between the relative abundance of Acidaminococcaceae and body mass index (r=0642, P=0.010). Principal component analysis suggested that the relative abundances of Acidaminococcaceae and Prevotellaceae were associated with severe asthma. Moreover, we found that class Betaproteobacteria, order Burkholderiales, and family Alcaligenaceae were significantly different among the groups defined by serum immunoglobulin E (IgE) levels.

Conclusions

Our findings suggest that altered gut microbiome compositions are involved in the severity of asthma and that there are specific bacteria related to different asthma phenotypes in terms of serum IgE levels.

Gut Microbiota, Probiotics, and Their Interactions in Prevention and Treatment of Atopic Dermatitis: A Review

Atopic dermatitis (AD) is a public health concern and is increasing in prevalence in urban areas. Recent advances in sequencing technology have demonstrated that the development of AD not only associate with the skin microbiome but gut microbiota. Gut microbiota plays an important role in allergic diseases including AD. The hypothesis of the “gut-skin” axis has been proposed and the cross-talk mechanism between them has been gradually demonstrated in the research. Probiotics contribute to the improvement of the intestinal environment, the balance of immune responses, regulation of metabolic activity. Most studies suggest that probiotic supplements may be an alternative for the prevention and treatment of AD. This study aimed to discuss the effects of probiotics on the clinical manifestation of AD based on gut microbial alterations. Here we reviewed the gut microbial alteration in patients with AD, the association between gut microbiota, epidermal barrier, and toll-like receptors, and the interaction of probiotics and gut microbiota. The potential mechanisms of probiotics on alleviating AD via upregulation of epidermal barrier and regulation of immune signaling had been discussed, and their possible effective substances on AD had been explored. This provides the supports for targeting gut microbiota to attenuate AD.

Delivery mode and gut microbial changes correlate with an increased risk of childhood asthma

There have been reports of associations between cesarean section delivery and the risk of childhood asthma, potentially mediated through changes in the gut microbiota. We followed 700 children in the Copenhagen Prospective Studies on Asthma in Childhood₂₀₁₀ (COPSAC₂₀₁₀) cohort prospectively from birth. We examined the effects of cesarean section delivery on gut microbial composition by 16S rRNA gene amplicon sequencing during the first year of life. We then explored whether gut microbial perturbations due to delivery mode were associated with a risk of developing asthma in the first 6 years of life. Delivery by cesarean section was accompanied by marked changes in gut microbiota composition at one week and one month of age, but by one year of age only minor differences persisted compared to vaginal delivery. Increased asthma risk was found in children born by cesarean section only if their gut microbiota composition at 1 year of age still retained a cesarean section microbial signature, suggesting that appropriate maturation of the gut microbiota could mitigate against the increased asthma risk associated with gut microbial changes due to cesarean section delivery.

Alteration of Intestinal Microbiota Composition in Oral Sensitized C3H/HeJ Mice Is Associated With Changes in Dendritic Cells and T Cells in Mesenteric Lymph Nodes

This research aimed to investigate the allergic reaction of C3H/HeJ mice after sensitization with ovalbumin (OVA) without any adjuvant and to analyze the association between intestinal microbiota and allergy-related immune cells in mesenteric lymph nodes (MLN). The allergic responses of C3H/HeJ mice orally sensitized with OVA were evaluated, and immune cell subsets in spleen and MLN and cytokines were also detected. The intestinal bacterial community structure was analyzed, followed by Spearman correlation analysis between changed gut microbiota species and allergic parameters. Sensitization induced a noticeable allergic response to the gavage of OVA without adjuvant. Increased levels of Th2, IL-4, CD103⁺CD86⁺ DC, and MHCII⁺CD86⁺ DC and decreased levels of Th1, Treg, IFN-γ, TGF-β1, and CD11C⁺CD103⁺ DC were observed in allergic mice. Furthermore, families of Lachnospiraceae, Clostridiaceae_1, Ruminococcaceae, and peprostreptococcaceae, all of which belonging to the order Clostridiales, were positively related to Treg and CD11C⁺CD103⁺ DC, while they were negatively related to an allergic reaction, levels of Th2, CD103⁺CD86⁺ DC, and MHCII⁺CD86⁺ DC in MLN. The family of norank_o_Mollicutes_RF39 belonging to the order Mollicutes_RF39 was similarly correlated with allergic reaction and immune cells in MLN of mice. To sum up, allergic reactions and intestinal flora disturbances could be induced by OVA oral administration alone. The orders of Clostridiales and Mollicutes_RF39 in intestinal flora are positively correlated with levels of Treg and CD11C⁺CD103⁺ DC in MLN of mice.

Probiotic mixture reduces gut inflammation and microbial dysbiosis in children with atopic dermatitis

BACKGROUND

Recent data suggested that dysbiosis of the gut microbiome is associated with childhood allergic diseases. Oral administration of probiotic formulations may improve the severity of atopic dermatitis (AD) by restoring imbalanced gut microbiota and reducing intestinal inflammation in children.

OBJECTIVES

The aim of this study was to investigate the effects of a probiotic mixture on the clinical severity of AD, gut inflammatory markers and alterations in microbiome dysbiosis in children with AD.

METHODS

A total of 25 subjects were enrolled in this study and administered with a mixture of probiotic strains consisting of Lactobacilli and Bifidobacteria for 4 weeks. The clinical efficacy of the probiotic mixture was assessed using SCORAD index and TEWL. Faecal calprotectin levels were measured as a marker for intestinal inflammation. The composition and diversity of the gut microbiome were analysed using 16S rRNA pyrosequencing.

RESULTS

The SCORAD (38.9 ± 17.2 vs 29.0 ± 15.4, P < 0.001) and TEWL (58.3 ± 12.5 vs 27.3 ± 8.7 g/m² /h, P = 0.028) were significantly decreased after 4 weeks administration of the probiotic mixture. The faecal calprotectin level (121.5 [27.7-292.9] vs 37.0 μg/g [12.6-108.9 μg/g], P = 0.038) was significantly decreased. The α-diversity and composition of the gut microbiome were not significantly changed, but β-diversity was increased after 4 weeks.

CONCLUSIONS

The oral administration of the probiotic mixture was effective in reducing clinical severity and intestinal inflammation in children with AD. Gut microbial diversity was slightly increased after administration of the probiotic mixture. The results of this study suggest that a probiotic mixture can alleviate AD by decreasing inflammation and modulating the gut microbiota in children with AD.

Cistanche deserticola polysaccharides alleviate cognitive decline in aging model mice by restoring the gut microbiota-brain axis

Recent evidence suggests alterations in the gut microbiota-brain axis may drive cognitive impairment with aging. In the present study, we observed that prolonged administration of D-galactose to mice induced cognitive decline, gut microbial dysbiosis, peripheral inflammation, and oxidative stress. In this model of age-related cognitive decline, Cistanche deserticola polysaccharides (CDPS) improved cognitive function in D-galactose-treated mice by restoring gut microbial homeostasis, thereby reducing oxidative stress and peripheral inflammation. The beneficial effects of CDPS in these aging model mice were abolished through ablation of gut microbiota with antibiotics or immunosuppression with cyclophosphamide. Serum metabolomic profiling showed that levels of creatinine, valine, L-methionine, o-Toluidine, N-ethylaniline, uric acid and proline were all altered in the aging model mice, but were restored by CDPS. These findings demonstrated that CDPS improves cognitive function in a D-galactose-induced aging model in mice by restoring homeostasis of the gut microbiota-brain axis, which alleviated an amino acid imbalance, peripheral inflammation, and oxidative stress. CDPS thus shows therapeutic potential for patients with memory and learning disorders, especially those related to gut microbial dysbiosis.

A Combined Analysis of Gut and Skin Microbiota in Infants with Food Allergy and Atopic Dermatitis: A Pilot Study

The gut microbiota in patients with food allergy, and the skin microbiota in atopic dermatitis patients differ from those of healthy people. We hypothesize that relationships may exist between gut and skin microbiota in patients with allergies. The aim of this study was to determine the possible relationship between gut and skin microbiota in patients with allergies, hence simultaneous analysis of the two compartments of microbiota was performed in infants with and without allergic symptoms. Fifty-nine infants with food allergy and/or atopic dermatitis and 28 healthy children were enrolled in the study. The skin and gut microbiota were evaluated using 16S rRNA gene amplicon sequencing. No significant differences in the α-diversity of dermal or fecal microbiota were observed between allergic and non-allergic infants; however, a significant relationship was found between bacterial community structure and allergy phenotypes, especially in the fecal samples. Certain clinical conditions were associated with characteristic bacterial taxa in the skin and gut microbiota. Positive correlations were found between skin and fecal samples in the abundance of Gemella among allergic infants, and Lactobacillus and Bacteroides among healthy infants. Although infants with allergies and healthy infants demonstrate microbiota with similar α-diversity, some differences in β-diversity and bacterial species abundance can be seen, which may depend on the phenotype of the allergy. For some organisms, their abundance in skin and feces samples may be correlated, and these correlations might serve as indicators of the host's allergic state.

Serum cytokine patterns are modulated in infants fed formula with probiotics or milk fat globule membranes: A randomized controlled trial

Background

Proteins and lipids of milk fat globule membrane (MFGM) and probiotics are immunomodulatory. We hypothesized that Lactobacillus paracasei ssp. paracasei strain F19 (F19) would augment vaccine antibody and T helper 1 type immune responses whereas MFGM would produce an immune response closer to that of breastfed (BF) infants.

Objective

To compare the effects of supplementing formula with F19 or bovine MFGM on serum cytokine and vaccine responses of formula-fed (FF) and BF infants.

Design

FF infants were randomized to formula with F19 (n = 195) or MFGM (n = 192), or standard formula (SF) (n = 194) from age 21±7 days until 4 months. A BF group served as reference (n = 208). We analyzed seven cytokines (n = 398) in serum at age 4 months using magnetic bead-based multiplex technology. Using ELISA, we analyzed anti-diphtheria IgG (n = 258) and anti-poliovirus IgG (n = 309) concentrations in serum before and after the second and third immunization, respectively.

Results

Compared with SF, the F19 group had greater IL-2 and lower IFN-γ concentrations (p<0.05, average effect size 0.14 and 0.39). Compared with BF, the F19 group had greater IL-2, IL-4 and IL-17A concentrations (p<0.05, average effect size 0.42, 0.34 and 0.26, respectively). The MFGM group had lower IL-2 and IL-17A concentrations compared with SF (p<0.05, average effect size 0.34 and 0.31). Cytokine concentrations were comparable among the MFGM and BF groups. Vaccine responses were comparable among the formula groups.

Conclusions

Contrary to previous studies F19 increased IL-2 and lowered IFN-γ production, suggesting that the response to probiotics differs across populations. The cytokine profile of the MFGM group approached that of BF infants, and may be associated with the previous finding that infectious outcomes for the MFGM group in this cohort were closer to those of BF infants, as opposed to the SF group. These immunomodulatory effects support future clinical evaluation of infant formula with F19 or MFGM.